1. Field of the Invention
This invention relates to alkali soluble styrene allyl alcohol copolymers and more particularly to trimellitic acid monoesters of styrene allyl alcohol copolymers and to the use of these copolymers in aqueous and organic solvent coating compositions as well as to coating compositions containing these copolymers and crosslinking resins such as aminoplasts, epoxies and reactive polymers.
2. Description of the Prior Art
Resinous polyols base upon styrene and allyl alcohol are commercial products which have found use in the surface coating industry both as chemical intermediates for preparation of fatty esters or polyesters and as hard resin components wherein the polyol may or may not be reacted in situ with other components of the coating. Introduction of one or more carboxyl groups into the polyol molecule via half acid ester formation with a suitable organic anhydride renders it soluble in aqueous alkali and could expand the potential use of the copolymers in coatings especially those designed for pollution control.
Such carboxylated polyols prepared by reaction of phthalic anhydride or succinic anhydride with styrene allyl alcohol copolymers have been described in U.S. Pat. No. 3,218,282. However, when these carboxylated polyols are used in aqueous coating formulations they suffer from disadvantages of instability manifested by increased viscosity or gelation and they provide surface coatings which are inadequate to a greater or lesser degree in solvent resistance, hardness and gloss.
A need therefore, exists for a carboxylated styrene allyl alcohol copolymer which is stable in viscosity and free from gelation in aqueous solution.
A further need exists for a carboxylated styrene allyl alcohol copolymer which can be cured to provide coatings which are solvent resistant, hard and glossy.
A further need exists for a carboxylated styrene allyl alcohol copolymer which can be formulated with epoxy resins, aminoplasts and reactive polyester and acrylic resins to give coatings of superior gloss, hardness and solvent resistance.